ATB shock absorber

Abstract

The headset of a conventional All Terrain Bicycle is modified to permit the load supported by the front wheel to be transferred to the bicycle frame through a column of compressed air to minimize the shock and vibration to the rider when riding over rough ground. A valve matching those in the bicycle tires is located on the centerline of the steering axis above the handle bar stem and permits the compressed air pressure to be adjusted for different rider weights through use of a conventional bicycle pump. The typical air pressure required is less than the tire pressure. This IMPROVED ATB SHOCK ABSORBER includes provisions for hydraulically damping the air spring motion. The shock absorber design should permit hard use for long periods without maintenance.

I claim: 
     
       1. In an All Terrain Bicycle with a conventional frame including a head tube and a front fork, an ATB Shock Absorber providing an improved means of shock and vibration isolation and comprising: a separate steering tube mounted on angular contact ball bearings in said head tube;   a fork tube slidably mounted inside said steering tube with a means for transferring torque from said steering tube to said fork tube;   a fork crown rigidly fastened on the lower end of said fork tube with a means for sealing the lower end of said fork tube.   a fork tube extension rigidly fastened on the upper end of said fork tube and slidably mounted inside said steering tube, with a sealant means for sealing against the loss of compressed air between said fork tube and said fork tube extension;   a seal installed on the upper end of said fork tube extension preventing the loss of compressed air between said fork tube extension and said steering tube;   a plug rigidly clamped in the upper end of said steering tube and a means for sealing between said plug and said steering tube against the loss of compressed air;   a damper tube rigidly clamped to said plug with a length of said damper tube extending up through the center of said plug, and a length of said damper tube extending down inside the upper end of said fork tube;   a means for sealing against the loss of compressed air between said damper tube and said plug;   a floating piston slidably mounted on said damper tube with a means for preventing the passage of any compressed air or any hydraulic fluid past said floating piston;   a spring holding said floating piston against a damper head fastened in the lower end of said damper tube.   a pneumatic valve installed inside the upper end of said damper tube with an air passageway connecting said pneumatic valve with the inside of said steering tube;   a handlebar stem rigidly clamped to said plug with a short length of the damper tube extending above said handlebar stem;   a short length of the upper end of said fork tube extension having reduced inside diameter;   a portion of said plug with a reduced outside diameter extending a short distance down from the top end of said steering tube with the upper end of said fork tube extension sliding over said reduced outside diameter portion of said plug near the upper end of the shock absorber stroke;   a seal on said plug trapping an annular volume of air between said plug and said fork tube extension near the end of the shock absorber stroke; and   an elastomeric boot installed between said steering tube and said fork tube to prevent the intrusion of dirt.   
     
     
       2. An Improved ATB Shock Absorber according to claim 1 wherein said means for transferring torque from said steering tube to said fork tube includes an inward facing flange on the lower end of said steering tube; multiple axial slots through said inward facing flange; and multiple axial ribs on said fork tube extending up through said axial slots. 
     
     
       3. An Improved ATB Shock Absorber according to claim 1 wherein said means for sealing between said fork tube and said fork tube extension includes external threads on the upper end of said fork tube engaging internal threads on the lower end of said fork tube extension with a suitable sealant on said threads. 
     
     
       4. An Improved ATB Shock Absorber according to claim 1 wherein said means for sealing the lower end of said fork tube includes internal threads on said fork tube engaging external threads on a flanged plug with said plug clamping said fork tube 1 to said fork crown, and with a suitable sealant on said threads.